Control valve assembly

Abstract

A control valve assembly incorporates direct metal-to-metal engagement between a casing of a temperature-responsive valve actuator and a piston guide to promote ease and accuracy of calibration. In addition, a substantially frictionless override feature is incorporated in the assembly to effect pressure relief and to accommodate thermal excursion of the valve actuator beyond the travel required to effect the desired valve movement.

I claim: 
     
       1. A temperature and pressure responsive fluid flow control assembly comprising a temperature responsive valve actuator having a heat conductive casing containing a thermally expansible material, a housing having a chamber therein, the housing including a cup of stamped metal construction having an apertured end wall defining a first end wall of the housing and a side wall having openings therein defining side wall openings for the housing, said first apertured end wall of the housing serving as a seat for the valve actuator casing in a normal operating position, the valve actuator casing being received within the housing chamber for movement away from its normal operating position toward a second end wall of the housing opposite its said first end wall, an override spring urging the casing toward said normal operating position, the spring having opposite ends seated against said second end wall of the housing and against a radial shoulder formed on the casing of the valve actuator, a tubular guide secured to the casing to extend from the chamber through said first apertured end wall of the housing, a piston slidably mounted within the guide and having an end projecting from the guide, said projecting end of the piston carrying a valve member for movement between closed and open positions, the valve actuator casing having an end extending beyond its said radial shoulder and surrounded solely by the coils of the override spring with the end of the valve actuator casing in spaced relation to a confronting side wall of the housing and its said second end wall in said normal operating position of the valve actuator to permit substantially frictionless movement of the casing away from its said normal operating position against the force of the override spring to balance fluid pressure force on the valve member for effecting pressure relief. 
     
     
       2. The assembly of claim 1 wherein the valve actuator casing and the guide are movable in unison relative to the piston against the force of said override spring when the valve member is in closed position to accommodate additional thermal excursion of the thermally expansible material. 
     
     
       3. The assembly of claim 1 further including a retainer of stamped metal construction fixed to the piston adjacent its projecting end, a bracket fixed to the retainer and supported for movement on the guide, and a piston return spring having its opposite ends seated against the bracket and the guide. 
     
     
       4. The assembly of claim 1 wherein a diaphragm extends across abutting ends of the casing and guide, the abutting ends of the casing and guide including spacing means for ensuring direct abutting metal-to-metal engagement therebetween and for establishing a gap wherein a peripheral edge of the diaphragm is clamped therebetween.